JP5905694B2 - A computed tomography scanner with a dynamic collimator for cardiac CT imaging with wide coverage and low dose - Google Patents

Description

  Embodiments of the present invention generally relate to diagnostic imaging, and more specifically may have high temporal resolution, reduced image artifacts due to missing data and longitudinal truncation, and reduced radiation dose. It relates to a possible computed tomography (CT) imaging method and apparatus.

  Typically, in computed tomography (CT) imaging systems, an x-ray source emits a fan-shaped beam toward a subject or object such as a patient or baggage. In the following, terms such as “subject”, “target”, and “object” shall include any object that can be imaged. The beam enters the array of radiation detectors after being attenuated by the subject. The intensity of the attenuated beam radiation received at the detector array typically depends on the amount of attenuation of the X-ray beam by the subject. Each detector element of the detector array generates a separate electrical signal indicative of the attenuated beam received by each detector element. The electrical signal is transmitted to the data processing system and analyzed, from which it ultimately forms an image.

  In general, the x-ray source and detector array rotate around the gantry around the subject in the imaging plane. The x-ray source typically includes an x-ray tube that emits an x-ray beam at the focal point. An X-ray detector typically includes a collimator that collimates an X-ray beam received at the detector, a scintillator that is provided adjacent to the collimator and converts X-rays into optical energy, and optical energy from the adjacent scintillator. And a photodiode for generating an electrical signal therefrom.

  Typically, each scintillator in the scintillator array converts x-rays into light energy. Each scintillator emits light energy to an adjacent photodiode. Each photodiode detects light energy and generates a corresponding electrical signal. The output of the photodiode is then transmitted to the data processing system for image reconstruction.

  One important latest application of CT imaging is its use in cardiac imaging. However, cardiac imaging techniques such as coronary CT angiography pose unique technical problems, one of which is the need for high temporal resolution to avoid image motion artifacts. is there. One way to achieve such high temporal resolution is to use a wide coverage multi-row detector CT (MDCT) system that scans the entire cardiac region within a single gantry rotation. In this document, a broad coverage refers to the irradiation range of the X-ray beam in the longitudinal direction that can cover (cover) most of the human heart within the range of one axial rotation. Typically, only data from about one half of the scan is used for image reconstruction in order to preserve temporal resolution. Unfortunately, however, such cardiac half-scan imaging methods face significant missing data and longitudinal truncation problems when large x-ray cone beam angles are large. Cone beam artifacts resulting from this cardiac half-scan method are easily observed in the reconstructed image and significantly degrade the image quality.

  To alleviate the missing data and longitudinal truncation problems associated with the cardiac half-scan technique described above, the use of wide-coverage full-scan cardiac imaging is one solution (but half-scan reconstruction). Method). This wide-coverage full scan cardiac imaging provides a way to maintain temporal resolution while mitigating the missing data and longitudinal truncation problems associated with half scan imaging. However, full scan cardiac imaging administers a greater dose of radiation to the subject compared to half scan cardiac imaging. In fact, the radiation dose in full scan cardiac imaging corresponds to a 50% (or even greater) increase in radiation dose over half scan cardiac imaging. Conventional full scan cardiac imaging is not ideal, even if every effort is made to minimize the amount of radiation and scan time a patient is irradiated.

  Therefore, it is desirable to design a CT imaging apparatus and method that can have high temporal resolution, missing data and reduced image artifacts due to longitudinal truncation, and reduced radiation dose.

  One embodiment of the present invention is configured to have a gantry having an opening that accommodates a subject to be scanned, and to be disposed inside the gantry so as to project an X-ray cone beam onto the subject when CT data is acquired. The present invention relates to a computed tomography (CT) scanner that includes an X-ray source that is configured and a detector array configured to detect X-rays that pass through a subject. The CT scanner further includes a dynamic collimator disposed in the vicinity of the X-ray source, and a controller, which rotates the X-ray source around the subject, A single rotation is divided into a first half scan and a second half scan, the first imaging data set is acquired during the first half scan, and the second imaging is performed during the second half scan. It is configured to obtain a data set. The controller further acquires image data from one of the first half scan and the second half scan, and then acquires image data from the other of the first half scan and the second half scan. At the same time, a dynamic collimator is placed so that the dynamic collimator blocks the central portion of the x-ray beam emitted by the x-ray source over one of the first half scan and the second half scan. The CT image is reconstructed using the first imaging data set and the second imaging data set.

  Another embodiment of the invention relates to a method of cardiac CT imaging, which method rotates an x-ray source through a series of projection angles around a scanned subject along an annular rotation path. A single rotation of the X-ray source is divided into a first half scan and a second half scan, and a rotating step, and a first imaging data set from the first half scan. And obtaining a second imaging data set from the second half scan. The method further includes the first half scan and the second half scan to block a central portion of the x-ray beam emitted by the x-ray source over one of the first half scan and the second half scan. After completing the acquisition of image data from one of the half scans, placing a collimator simultaneously with the start of acquiring image data from the other of the first half scan and the second half scan; And reconstructing a CT image using the second imaging data set and the second imaging data set.

  Another embodiment of the present invention is a rotary gantry having an opening that accommodates a subject to be scanned, and an X-ray beam that is disposed inside the rotary gantry and projects an X-ray beam onto the subject when CT data is acquired. A CT imaging device comprising: an X-ray source configured to be configured; and a collimator disposed in the vicinity of the X-ray source and configured to be movably disposed in a path of an X-ray projection beam It is about the system. The CT imaging system further includes a computer that rotates the X-ray source all around the subject, the rotation of the X-ray source being in the first half scan and the second half scan. It is divided and programmed to obtain a first imaging data set from the first half scan and a second imaging data set from the second half scan. The computer further includes acquiring the imaging data from one of the first half scan and the second half scan after acquiring the imaging data from one of the first half scan and the second half scan. At the start, the collimator is moved to block the central part of the X-ray beam emitted by the X-ray source throughout the acquisition of imaging data from the other of the first half scan and the second half scan Arranged freely and programmed to reconstruct a CT image using the first imaging data set and the second imaging data set.

  Various other features and advantages will be made apparent from the following detailed description and the drawings.

The drawings show a preferred embodiment presently contemplated for carrying out the invention.
1 is a sketch of a CT imaging system. It is a block schematic diagram of the system shown in FIG. FIG. 6 is a perspective view of one embodiment of a CT system detector array. FIG. 6 is a perspective view of one embodiment of a detector. FIG. 6 is a schematic diagram of a first half scan of a longitudinally wide detector approach to cardiac CT imaging according to an embodiment of the present invention. FIG. 4 is a schematic diagram of a second half scan of a longitudinally wide detector approach to cardiac CT imaging according to one embodiment of the present invention. 4 is a flowchart illustrating a method of CT imaging according to an embodiment of the present invention. 1 is a sketch of a CT system used with a non-invasive package inspection system.

  The operating environment of the present invention will be described in the context of a wide coverage multi-row detector computed tomography (CT) system. However, those skilled in the art will recognize that the present invention is equally applicable for use in other multi-slice configurations. The present invention will also be described in relation to X-ray detection and conversion. However, those skilled in the art will further appreciate that the present invention is equally applicable to the detection and conversion of other high frequency electromagnetic energy. Although the present invention will be described with respect to a “third generation” CT scanner, the present invention is equally applicable to other CT systems.

  In FIG. 1, a computed tomography (CT) imaging system 10 is shown as including a gantry 12 typical of a “third generation” CT scanner. The gantry 12 has an x-ray source 14 that projects an x-ray beam toward a detector assembly or post patient collimation 18 provided on the opposite side of the gantry 12. Referring to FIG. 2, the detector assembly 18 is formed by a plurality of detectors 20 and a data acquisition system (DAS) 32. A plurality of detectors 20 sense the projected x-rays 16 that pass through the patient 22, and the DAS 32 converts the data into digital signals for subsequent processing. Each detector 20 generates an analog electrical signal that represents the intensity of the incident x-ray beam and thus the attenuated beam transmitted through the patient 22. The gantry 12 and components mounted on the gantry 12 rotate around the rotation center 24 during one scan for acquiring X-ray projection data.

  The rotation of the gantry 12 and the operation of the X-ray source 14 are controlled by the control mechanism 26 of the CT system 10. The control mechanism 26 includes an X-ray controller 28 and a gantry motor controller 30. The X-ray controller 28 supplies power signals and timing signals to the X-ray source 14, and the gantry motor controller 30 The rotational speed and position of the gantry 12 are controlled. An image reconstructor 34 receives sampled and digitized x-ray data from DAS 32 and performs high speed reconstruction. The reconstructed image is applied as an input to the computer 36, which causes the mass storage device 38 to store the image.

  The computer 36 also receives commands and scanning parameters from an operator via a console 40 having some form of operator interface such as a keyboard, mouse, voice activated controller, or any other suitable input device. receive. The attached display 42 allows the operator to observe the reconstructed image and other data from the computer 36. The instructions and parameters supplied by the operator are used by computer 36 to provide control signals and information to DAS 32, X-ray controller 28 and gantry motor controller 30. In addition, the computer 36 operates the table motor controller 44 that controls the electric table 46 to place the patient 22 and the gantry 12. Specifically, the table 46 moves the patient 22 in whole or in part through the gantry opening 48 of FIG.

  As shown in FIG. 3, the detector assembly 18 includes a rail 17 with a collimating blade or plate 19 disposed therebetween. The plate 19 is arranged to collimate the x-ray 16 before the x-ray beam is incident on the detector 20 of FIG. In one embodiment, detector assembly 18 includes 57 detectors 20, each detector 20 having a pixel element 50 with an array size of 64 × 16. As a result, the detector assembly 18 has 64 rows and 912 columns (16 × 57 detectors), allowing each simultaneous rotation of the gantry 12 to collect data for 64 simultaneous slices. I have to. In order to achieve a long longitudinal coverage so as to cover the entire human heart in one revolution, typically more than 64 rows of detectors are required. The number of required detector rows is a function of the required coverage and the width of the detector rows.

  Referring to FIG. 4, the detector 20 includes a DAS 32, and each detector 20 includes a number of detector elements 50 configured as a pack 51. The detector 20 includes pins 52 disposed within the pack 51 with respect to the detector element 50. The pack 51 is disposed on a back-illuminated diode array 53 having a plurality of diodes 59. Next, the back illuminated diode array 53 is disposed on the multilayer substrate 54. A spacer 55 is disposed on the multilayer substrate 54. The detector element 50 is optically coupled to the back illuminated diode array 53, which is then electrically coupled to the multilayer substrate 54. A soft (flex) circuit 56 is attached to the surface 57 of the multilayer substrate 54 and the DAS 32. The detector 20 is placed inside the detector assembly 18 through the use of pins 52.

  In operation of one embodiment, X-rays incident inside the detector element 50 generate photons, and the photons traverse the pack 51 to generate an analog signal that is backlit diode array 53. Is detected in the diode inside. The generated analog signal passes through the multi-layer substrate 54 and through the flex circuit 56 to the DAS 32 where the analog signal is converted to a digital signal.

  As mentioned above, one of the important latest applications of computed tomography is its use in cardiac imaging. Since the heart motion is fast and substantially steady, cardiac CT imaging uses a fast temporal acquisition speed to avoid motion artifacts in the reconstructed image. To achieve such high temporal resolution, various advanced acquisition techniques have been developed for cardiac imaging, including high gantry rotation speed, wide longitudinal detector coverage, and multiple X-ray sources. Yes. Describing an approach that is particularly wide in the longitudinal direction, a single single axis rotation around the subject of the x-ray source is expected to allow imaging of the entire heart for the majority of the patient population. .

  Traditionally, cardiac imaging is performed using a half-scan acquisition mode that allows the imaging data necessary to reconstruct an image to be acquired from essentially one-half of a full gantry rotation. However, due to the large cone beam angle present in the longitudinally wide detector approach, there may be significant cone beam artifacts in the image formed using the half scan acquisition mode. The use of full scan acquisition mode can reduce cone beam artifacts present in the image, but this is at the cost of adding radiation dose to the subject.

  FIG. 5 shows a schematic diagram of a longitudinal detector approach to the above-described cardiac CT imaging. FIG. 5 represents a first half-scan acquisition according to an embodiment of the invention as described below.

  The x-ray source 200 emits a cone-shaped x-ray beam 201 through a bow tie filter 202 that removes these photons before the low energy photons emitted by the x-ray source 200 reach the scan target. Absorb. Both the X-ray source 200 and the bow tie filter 202 rotate axially around the Z axis of the imaging volume 204. FIG. 5 shows an X-ray source 200 and bowtie filter 202 rotated only 180 ° about the Z axis, but this illustration is merely to show the coverage of the cone-shaped beam 201 through the scan. It should be understood that the x-ray source 200 and bowtie filter 202 are capable of 360 ° rotation about the imaging volume 204.

  For cardiac CT imaging, the imaging volume 204 corresponds to the entire cardiac region and is the region that is intended to be reconstructed after a single rotation around the Z axis of the x-ray source 200 and bowtie filter 202. In the example shown in FIG. 5, the imaging volume 204 has dimensions of 160 mm (w = 160 mm) and a total diameter of 250 mm (d = 250 mm) in the longitudinal direction, but the imaging volume 204 is not limited to such dimensions. I want you to understand. Furthermore, although the distance from the X-ray source 200 to the Z axis in FIG. 5 is 610 mm, it should be understood that this distance is likewise not limited to such dimensions.

  In a full scan acquisition of the imaging volume 204, the X-ray source 200 can be rotated about the imaging volume 204 with full axis rotation (ie, 360 °), and imaging data from this full scan can be utilized. The image representing 204 is reconstructed. After the imaging data is acquired in the first half scan (ie, the first 180 ° of full axis rotation + fan angle), the imaging data having a projection angle complementary to the projection angle of the first half scan is Acquired in two half scans (ie, a second 180 ° section with full axis rotation). In this way, full scan acquisition provides the maximum range of data used for image reconstruction, which is useful for reconstructing images with reduced artifacts. For example, referring to FIG. 5, full scan acquisition is achieved with a total scan coverage of 360 ° in region 206 of imaging volume 204, a scan coverage greater than 180 ° in region 208, and 180 ° in region 210. Also expect a small scan coverage. In order for the reconstructed image to have little or no cone beam artifacts, a scan coverage of at least 180 ° is desirable, and such scan coverage is substantially obtained using full scan acquisition. In fact, using the example shown in FIG. 5, more than 98% of the coverage is provided via full scan acquisition, and only the smallest area 210 is less than 180 ° scan coverage under these conditions. I will provide a.

  While a full scan acquisition can successfully acquire an image with minimal cone beam artifacts, such full scan acquisition also administers an additional dose of radiation that is undesirable to the subject being scanned. Alternatively, the half-scan acquisition approach can be used to reduce radiation dose, but such an approach itself has substantially less coverage compared to full scan acquisition due to image reconstruction. Only make the data available. As mentioned above, a scan coverage of at least 180 ° is desirable for image reconstruction. Using only half-scan acquisition, the possible data range is much smaller, so a significant portion of the imaging volume 204 will contain insufficient data for image reconstruction. For example, referring again to FIG. 5, region 206 of imaging volume 204 has a scan coverage that is greater than 180 ° using a half-scan acquisition approach, while region 208 is a scan coverage that is less than 180 °. And region 210 has a scan coverage that is much smaller than 180 °, resulting in approximately 86% of the total coverage data (for coverage data greater than 98% using full scan acquisition). Compared to). Lack of scan coverage with traditional half-scan acquisition alone leads to undesirable cone beam artifacts, so the half-scan acquisition approach is wide coverage when cone beam artifacts are the main concern Is not interesting for use in heart imaging.

  Thus, while FIG. 5 illustrates a first half-scan acquisition according to one embodiment of the present invention, it allows acquisition of data sufficient for low artifact image reconstruction and yet the additional scan object is administered. In order to minimize the radiation dose, a second half-scan acquisition is desired. Embodiments of the present invention achieve such image data acquisition methods using respective first and second half-scan acquisitions, as further described below in connection with FIG.

  FIG. 6 shows a schematic diagram of second half-scan acquisition according to embodiments of the present invention. For consistency and clarity, common elements between FIGS. 5 and 6 share common reference numerals, and the purpose or meaning of each common element is not repeated here.

  As described above, with respect to FIG. 5, the image data from the first half scan is acquired by rotating the X-ray source 200 and the bow tie filter 202 about the Z axis of the imaging volume 204 to obtain the imaging data. Are acquired continuously during this first half-scan. The first half scan constitutes a 180 ° rotation about the Z axis with the fan angle of the X-ray beam. Since a scan cover range larger than 180 ° is obtained in the region 206, sufficient image data is acquired for the region 206 during the first half scan. However, in regions 208 and 210, insufficient data is acquired from the first half scan alone, and therefore full scan acquisition is more effective for effective overall image reconstruction of the imaging volume 204. Interesting.

  Thus, after acquisition of image data during the first half scan, the X-ray source 200 enters a second 180 ° axial rotation around the imaging volume 204, referred to as a second half scan. However, simultaneously with the start of image data acquisition in the second half scan, the dynamic collimator 212 effectively shuts off the central portion of the X-ray beam emitted from the X-ray source 200. 200 is movably disposed between the bow tie filter 202. Thus, during the second half-scan, the dynamic collimator 212 blocks much of the x-ray beam emitted from the x-ray source 200, but the outer portion of the x-ray beam (ie, outside the x-ray beam line 214). ) Is left to enter the scanning object. Redundant unnecessary image data from the area 206 that has already been acquired during the first half scan is not acquired during the second half scan, and image data from the areas 208 and 210 that are insufficiently sampled is the second. Still acquired during a half scan, which allows a data range of at least 180 ° to be acquired for most of the imaging volume 204. After acquisition of image data from both the first half scan and the second half scan, the CT image is reconstructed.

  The CT imaging techniques described above in connection with FIGS. 5 and 6 not only allow a sufficient data range to be acquired, but also substantially reduce the radiation dose to which the scanned object may be administered. Reduce to. In addition, when this technique is implemented for cardiac CT imaging at any gantry rotational speed, a complete full scan acquisition can be completed within a single heart rate, thereby avoiding motion artifacts. Achieving the required high time resolution.

  The dynamic collimator 212 is preferably formed of a highly attenuating material (e.g., tungsten) and enables effective blocking of a substantial portion of the x-ray beam emitted by the x-ray source 200. Although the term “collimator” is used, the dynamic collimator 212 does not shape the X-ray beam in the conventional sense, but instead makes the X-ray beam incident on the scanning object while the outer portion of the X-ray beam is incident on the scanning object. The substantial central part of (ie 80%) is blocked. Unlike conventional collimators used for CT imaging, the dynamic collimator 212 is also formed as a single unit. Furthermore, the dynamic collimator 212 is freely movable between the X-ray source 200 and the bow tie 202 after the first half scan, simultaneously with the start of the second half scan, using any suitable actuation means. Can be arranged. However, in the above-described example, it is defined that the dynamic collimator 212 is arranged at the time of the second half scan, but the present invention is not limited to this. That is, the dynamic collimator 212 is arranged so as to block a part of the X-ray beam at the time of the first half scan, and is not arranged so as to block a part of the X-ray at the time of the second half scan. May be. Further, the dynamic collimator 212 may be arranged to block a portion of the x-ray beam during any period of full scan.

  If the dynamic collimator 212 is not used during the second half-scan, the radiation dose can be greater, for example, by more than 50% at the time of full scan acquisition than simply performing a half scan acquisition for the same coverage. . However, if the dynamic collimator 212 is used to block, for example, 80% of the x-ray beam during the second half scan, the object being imaged is uniformly covered by at least 180 ° sampling. That will be certain. This approach is equivalent to a radiation dose reduction of about 30% over conventional full scan acquisition. Such substantial reduction in radiation dose, coupled with high temporal resolution and cone beam artifact reduction, makes the wide-coverage full scan acquisition approach described with respect to the present invention an interesting option for cardiac CT imaging. And

  FIG. 7 illustrates a method 300 for CT imaging according to one embodiment of the present invention. The method 300 begins at block 302 by rotating an x-ray source around a scanned subject (eg, a patient) along an annular path. At block 304, a first imaging data set is obtained from a first half scan from an x-ray source. Next, in block 306, a dynamic collimator is arranged simultaneously with the start of acquisition of imaging data from the second half scan after completion of acquisition of imaging data during the first half scan. As described above, the dynamic collimator is configured to block a substantial portion of the x-ray beam emitted by the x-ray source during the second half scan. At block 308, a second set of imaging data is acquired from the second half scan, thereby completing the full scan acquisition of the imaging data. Finally, at block 310, a CT image is reconstructed using the acquired first and second imaging data sets.

  The above examples are particularly relevant to cardiac CT imaging, but the present invention is not so limited. The present invention can be applied to other forms of CT imaging, particularly CT imaging where reduced or limited radiation dose is desired, including neurological studies and pediatric scanning.

  Referring to FIG. 8, a parcel / baggage inspection system 100 includes a rotating gantry 102 having an opening 104 through which a parcel or baggage can pass. The rotating gantry 102 contains a high frequency electromagnetic energy source 106 and a detector assembly 108 having a scintillator array comprised of scintillator cells similar to those shown in FIG. Also provided is a conveyor system 110 that includes a conveyor belt 112 that is supported by structure 114 and that automatically and continuously passes parcels or baggage 116 through openings 104 for scanning. It is out. The object 116 is fed into the opening 104 by the conveyor belt 112, then the imaging data is acquired and the parcel 116 is removed from the opening 104 by the conveyor belt 112 in a controlled and continuous manner. As a result, postal inspectors, baggage unloaders, and other security personnel can non-invasively inspect the contents of parcels 116 for explosives, blades, guns, smuggled goods, and the like.

  The technical contribution of the disclosed method and apparatus is that of computed tomography (CT) imaging that can have high temporal resolution, reduced image artifacts due to missing data and longitudinal truncation, and reduced radiation dose. To provide a computer implemented to perform the method.

One skilled in the art will recognize that each embodiment of the present invention can be coupled to and controlled by a computer readable storage medium that stores a computer program. A computer-readable storage medium includes a plurality of components, such as one or more of electronic components, hardware components, and / or computer software components. These components are one or more computers that typically store instructions, such as software, firmware, and / or assembly language, that execute one or more implementations or portions of embodiments in a chain. A readable storage medium may be included. These computer readable storage media are typically non-transitory and / or tangible. Examples of such computer-readable storage media include computer recordable data storage media and / or storage devices. The computer readable storage medium may use, for example, one or more of magnetic, electrical, optical, biological, and / or atomic data storage media. Further, such media may take the form of, for example, floppy disks ("Floppy" is a trademark) , magnetic tape, CD-ROM, DVD-ROM, hard disk drive, and / or electronic memory. Other forms of non-transitory and / or tangible computer-readable storage media not listed may be used with each embodiment of the invention.

  A number of such components can be combined or divided in a system implementation. Further, such components may include a set and / or series of computer instructions written or embodied in any of a number of programming languages, as will be appreciated by those skilled in the art. In addition, one or more implementations or one or more portions of the embodiments form a chain when executed by one or more computers using other forms of computer readable media such as carrier waves. A computer data signal representing a sequence of instructions that cause the one or more computers to perform can be implemented.

  Accordingly, in one embodiment of the present invention, a gantry having an opening that accommodates a subject to be scanned and a gantry disposed inside the gantry so as to project an X-ray cone beam onto the subject when CT data is acquired. The present invention relates to a computed tomography (CT) scanner including an X-ray source configured as described above and a detector array configured to detect X-rays transmitted through a subject. The CT scanner further includes a dynamic collimator disposed in the vicinity of the X-ray source, and a controller, which rotates the X-ray source around the subject, A single rotation is divided into a first half scan and a second half scan, the first imaging data set is acquired during the first half scan, and the second imaging is performed during the second half scan. It is configured to obtain a data set. The controller further acquires image data from one of the first half scan and the second half scan, and then acquires image data from the other of the first half scan and the second half scan. At the same time, a dynamic collimator is placed so that the dynamic collimator blocks the central portion of the x-ray beam emitted by the x-ray source over one of the first half scan and the second half scan. The CT image is reconstructed using the first imaging data set and the second imaging data set.

  Another embodiment of the invention relates to a method of cardiac CT imaging, which method rotates an x-ray source through a series of projection angles around a scanned subject along an annular rotation path. A single rotation of the X-ray source is divided into a first half scan and a second half scan, and a rotating step, and a first imaging data set from the first half scan. And obtaining a second imaging data set from the second half scan. The method further includes the first half scan and the second half scan to block a central portion of the x-ray beam emitted by the x-ray source over one of the first half scan and the second half scan. After completing the acquisition of image data from one of the half scans, placing a collimator simultaneously with the start of acquiring image data from the other of the first half scan and the second half scan; And reconstructing a CT image using the second imaging data set and the second imaging data set.

  Yet another embodiment of the present invention is a rotary gantry having an opening for accommodating a subject to be scanned, and an X-ray beam applied to the subject when CT data is acquired. CT imaging including an X-ray source configured to project and a collimator disposed in the vicinity of the X-ray source and configured to be movably disposed in the path of the X-ray projection beam・ It is about the system. The CT imaging system further includes a computer that rotates the X-ray source all around the subject, the rotation of the X-ray source being in the first half scan and the second half scan. It is divided and programmed to obtain a first imaging data set from the first half scan and a second imaging data set from the second half scan. The computer further includes acquiring the imaging data from one of the first half scan and the second half scan after acquiring the imaging data from one of the first half scan and the second half scan. At the start, the collimator can be moved to block the central portion of the x-ray beam emitted by the x-ray source throughout the acquisition of imaging data from the other of the first half scan and the second half scan And is programmed to reconstruct a CT image using the first imaging data set and the second imaging data set.

  This written description discloses the invention, including the best mode, and allows any person skilled in the art to make and use any device or system and perform any incorporated methods. Examples are used to make it possible to implement. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other instances have structural elements that do not differ from the written language of the claims, or include equivalent structural elements that have substantial differences from the written language of the claims. Are intended to be within the scope of the claims.

DESCRIPTION OF SYMBOLS 10 Computerized tomography (CT) imaging system 12 Gantry 14 X-ray source 16 Projected X-ray 17 Rail 18 Detector assembly 19 Collimating blade or plate 20 Detector 22 Patient 24 Center of rotation 26 Control mechanism 28 X-ray controller 30 Gantry motor controller 32 Data acquisition system (DAS)
34 Image Reconstructor 36 Computer 38 Mass Storage Device 40 Console 42 Display 44 Table Motor Controller 46 Electric Table 48 Gantry Opening 50 Detector Element 51 Pack 52 Pin 53 Back-illuminated Diode Array 54 Multilayer Substrate 55 Spacer 56 Soft circuit 57 Surface 59 Multiple diodes 100 Parcel / baggage inspection system 102 Rotating gantry 104 Opening 106 High frequency electromagnetic energy source 108 Detector assembly 110 Conveyor system 112 Conveyor belt 114 Structure 116 Parcel or baggage 200 X-ray source 201 Cone Shaped X-ray beam 202 Bowtie filter 204 Imaging volume 206, 208, 210 Region 212 Dynamic collimator 214 Line 300 CT imaging method

Claims (10)

A gantry (12) having an opening (48) for accommodating a subject (22) to be scanned;
An X disposed within the gantry (12) and configured to project an X-ray cone beam (201) onto the subject (22) when acquiring computerized tomography (CT) data. A source (14, 200);
A detector array (18) configured to detect X-rays transmitted through the subject (22);
A dynamic collimator (212) disposed in the vicinity of the X-ray source (14, 200);
A computed tomography (CT) scanner (10) comprising a controller (26), said controller (26) comprising:
The X-ray source (14, 200) is rotated around the subject (22), and a single rotation of the X-ray source (14, 200) causes a first half scan and a second half scan. Divided into
Obtaining a first imaging data set during the first half-scan,
Acquiring a second set of imaging data during the second half-scan,
After acquiring image data from one of the first half scan and the second half scan, acquisition of image data from the other of the first half scan and the second half scan. Concurrently with the start, the dynamic collimator (212) is placed, and the dynamic collimator (212) is arranged in the X-ray source (14, 200) over one of the first half scan and the second half scan. Is configured to block a central portion defined along the z-axis of the X-ray beam (201) emitted by
A computed tomography (CT) scanner (10) configured to reconstruct a CT image using the first imaging data set and the second imaging data set. The controller further includes a bowtie filter (202) disposed near the X-ray source (14, 200) and absorbing low energy photons before reaching the subject (22). The computer of claim 1, wherein the computer is configured to place the dynamic collimator (212) between the X-ray source (14, 200) and the bowtie filter (202). Computed tomography (CT) scanner. The computed tomography (CT) scanner according to claim 1 or 2, wherein the dynamic collimator (212) is formed of a material having high X-ray attenuation characteristics. The computed tomography (CT) scanner of claim 3, wherein the dynamic collimator (212) is made of tungsten. A computer formula according to any of the preceding claims, wherein the dynamic collimator (212) includes a single element configured to block a portion of the x-ray beam (201). Tomography (CT) scanner. The dynamic collimator (212), the only blocks the central portion, the outer portion of the X-ray beam (201) of the X-ray beam emitted by the X-ray source (14,200) (201) is the The computed tomography (CT) scanner according to claim 1, wherein the computed tomography (CT) scanner is arranged apart from the X-ray source (14, 200) so as to leave it to reach the subject. The dynamic collimator (212) is configured to block 80% of the X-ray beam (201) emitted by the X-ray source (14, 200) during the second half scan. A computed tomography (CT) scanner according to any of claims 1-6. The controller (26) is configured to rotate the x-ray source (14, 200) completely around the subject (22) within a single heartbeat range of the subject (22). A computed tomography (CT) scanner according to any one of the preceding claims. The controller (26) is based on the first imaging data set and the second imaging data set acquired from the full rotation of the X-ray source (14, 200) around the subject (22). 9. A computed tomography (CT) scanner according to any of claims 1 to 8, configured to reconstruct the CT image. A computed tomography (CT) scanner according to any preceding claim, wherein the detector array (18) is a multi-row detector array.